Tailing dams - practical problems of ageing

摘要

The first tailing dams in the Czech Republic storing flying ash started to operate at the end of fifties. After nearly 40 years of operation some problems have appeared frequently connected with the functioning of the drainage system. The paper describes the problem connected with "Debrne" tailing dam where strong erosion of the flying ash started after the local failure of the concrete drainage gallery at the bottom of the deposited flying ash. Therefore practical steps that were used to reach stable conditions are described in more detail. Between these steps belong closing the outlet from drainage gallery followed by pore pressure increase, installation of wells to decrease pore pressure, injection of the drainage gallery front at the place of local failure, closing the drainage gallery in the lower part respecting filtration criteria to ensure that the rest of the gallery will work as a drainage, reconstruction of the concrete gallery from this point to the outlet.